Motor graders are used primarily as finishing tools to sculpt a surface of terrain to a final arrangement. Rather than moving large quantities of earth in the direction of travel like other machines, such as a bulldozer, a motor grader typically moves relatively small quantities of earth from side to side. In other words, a motor grader typically moves earth across the area being graded, rather than straight ahead.
Conventional motor graders typically include a frame supported on spaced front and rear wheels, with a blade or mold board suspended below the frame between the front and rear wheels in a pulled arrangement. In order to allow the motor grader to move earth in a desired manner, the blade is adjustable in multiple dimensions. Generally, the blade is supported on a circle that is coupled to a drawbar suspended by struts below the frame between the front and rear wheels. The circle is mechanically engaged with the drawbar by a gearing mechanism. A hydraulic motor is disposed to rotate the circle relative to the drawbar in order to pivot the blade about an articulation axis.
The components of the rotation mechanism, including, for example, the worm gear drive and ring gear typically utilized to rotate the blade relative to the drawbar, as well as wear plates, may necessitate ongoing maintenance, particularly in view of their exposure to weather elements, as well dirt, gravel and the like from the surrounding terrain. Further, the rotation mechanism may present packaging challenges, and may limit degrees of movement. Additionally, the rotation mechanism may require specialized components, such as rotary hydraulic elements.
U.S. Pat. No. 4,074,768, which is likewise assigned to the assignee of this disclosure, is directed to a mechanism that alleviates some of these potential shortcomings by utilizing a blade support and control arrangement that includes a linkage arrangement that pushes, as opposed to pulls the blade. The arrangement disclosed in the '768 patent presents its own shortcomings, however, and may be unstable in some applications.
As a result, it is desirable to provide a blade mounting arrangement that eliminates or minimizes potential difficulties with existing systems.